Question

A cell supplies a current of 0.9 A through a $2\Omega$ resistor and 0.3 A through a $7\Omega$ resistor. What is the internal resistance of the cell?

• A. $0.5\Omega$
• B. $1\Omega$
• C. $1.2\Omega$
• D. $2\Omega$

Answer 1

Answer: (A)

$0.5\Omega$

Using the relation,$I=\frac{E}{(R+r)}$
We have,
$0.9=\frac{E}{(r+2)}$
$0.3=\frac{E}{(r+7)}$
On dividing both the equation it will give,
$r=0.5$ ohm.